Daily driver small block build

LA vs Magnum, you'll have to think what your whole package will be when you drop it in your Dart; and it's going to be the little things that add up and drive up your costs.
Things like:
Do you want an electric fuel pump, or do you want to stay with a mechanical pump? Magnums can be converted to mechanical, but you will need to source LA front components (timing cover, water pump, pulleys, accessories and brackets, and an early Magnum balancer with the bolt-on pulley) to do it; adding to the cost of the Magnum.
A Magnum, any Magnum, is going to require you to get a Magnum-compatible 4 bbl. manifold and a 360 passenger car oil pan, pickup, and dipstick/tube in order to fit your Dart, along with a non-EFI distributor.
Granted, most of this is a drop in the bucket if you can avoid having major machine work done by scoring a good condition Magnum, but it is something to keep in mind. The little things add up fast.
As far as HP, either Magnum or LA will get you there. With LAs/Magnums you can basically fart on them and make 300 hp, but as previously mentioned it's the 360/5.9's torque that will make you smile with a daily driver. Avoid the pitfall of thinking "bigger is better" with your build, and you'll be fine either way. Avoid the "bling" that doesn't add to performance or drivability (fancy cast valve covers and chrome thermostat necks don't add 1 single horsepower or mpg) to keep costs down.
Your build will ultimately hinge on what kind of deal you come across at the right price, That LA 360 needing a full rebuild at a premium price will pale in comparison to the 5.2 Magnum that some guy is selling dirt cheap because he pulled it out of his Ram to put in a Cummins...
My recipe?
Find an early/mid 90s van, 2wd pickup or Dakota with a 5.2 and a 32RH.
Front drive, fuel pump, and accessories from an LA, oil pan as mentioned.
LA roller block 360 cam, stock. (the cam's specs are enhanced by the Magnum's 1.6 rocker ratio vs. the LA's 1.5, and has the long snout to drive a fuel pump. No custom pushrods needed like a reground cam would require.)
Get HalifaxHops to curve you a distributor.
Chinese 4 bbl manifold with whatever flavor 600 cfm carb you prefer.
904 kickdown linkage to the 32RH.
Cheap azz generic Summit or Jeg's headers and exhaust kit.
You'll be breathin' on 300 easy, and the mild cam and lockup convertor of the 32RH will have you well over 20mpg all day long.